Revert "Do not handle fallback here, it should not happen"

This reverts commit fc8bcfcc.

weblate/trans/models/unit.py

@@ -150,6 +150,9 @@ class UnitManager(models.Manager):
             return self.filter(has_comment=True)
         elif rqtype in CHECKS or rqtype in ['allchecks', 'sourcechecks']:
             return self.filter_checks(rqtype, translation, ignored)
+        else:
+            # Catch anything not matching including 'all'
+            return self.all()
 
     def count_type(self, rqtype, translation):
         """